Release of Aspirin from Biodegradable Polyesterurethane Networks

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In this paper, the release of model drug aspirin (ASP) from biodegradable polyesterurethane networks was studied. Poly(D,L-lactide-co-glycolide)urethane (PULG) networks were prepared from hydroxyl telechelic star-shaped oligo(D,L-lactide-co-glycolide) coupled with 1,6-diisocyanate-2,2,4-trimethylhexane and 1,6-diisocyanate-2,4,4-trimethylhexane or isophorone diisocyanate. PULG networks turned from transparent to opaque after ASP loading. PULG networks with lower crosslinking density always resulted in higher drug loaded content. The results of differential scanning calorimetry (DSC) and scanning electron microscope (SEM) measurements demonstrated that ASP was uniformly distributed in the networks. The drug release courses of ASP from PULG networks in phosphate buffered saline pH = 7.0 at 37 °C could be divided into three stages. Firstly, ASP release was at approximately uniform rate from PULG networks; Secondly, the release rate obviously increased for the degradation of the PULG networks; Thirdly, the release rate decreased gradually because most of the ASP had diffused out of the PULG networks. The crosslinking density of polyesterurethane networks also affected drug release rate. The in vitro release test revealed that ASP accelerated the degradation process of PULG, which exhibited a typical erosion-controlled release mechanism.

Abstract: Hydroxyapatite (HA) has been widely used as bone grafts due to its chemical and structural similarities to the mineral phase of hard tissues. Applying the combination of osteogenic proteins with HA materials can accelerate bone regeneration in defective areas. The aim of the study was investigating the treatment of HA particles with different amino acids such as serine (Ser), asparagine (Asn), aspartic acid (Asp) and arginine (Arg) to enhance the adsorption ability of HA carrier for delivering therapeutic proteins in body. Results: The crystallinity of HA reduced when amino acids were added during HA preparation. Depending on the types of amino acid, the specific surface area of the amino acid-functionalized HA particles varied from 105 to 149 m2/g. Bovine serum albumin (BSA) and lysozyme were used as model proteins for adsorption study. The protein adsorption onto the surface of amino acid-functionalized HA depended on the polarities of HA particles, whereby positively charged Arg-HA had higher affinity towards BSA (0.269 mg/m2) compared to lysozyme (0.133 mg/m2). Alternatively, the binding affinity of lysozyme (0.2 mg/m2) onto the negatively charged Asp-HA was higher compared to BSA (0.129 mg/m2). The amino acids functionalized-HA particles that had higher proteins adsorption demonstrated a lower protein release rate.

Abstract: This paper reviewed our research progress in respects of th intercalation law of acetylsalicylic acid (ASP) with magnesium aluminate layered double hydroxide (LDH), the drug release mechanism and the tablet preparation effect of LDH-ASP system. We also discussed the propositions about the composite assembly rules, slow-release mechanism, and dosage form processing of the layered double hydroxide drug delivery system. Intercalation way and drug structure should be taken into consideration in assembly LDH-drugs system. The characteristic parameter of the composite LDH-drug reflected finely their loading efficiency and correlated definitely with drug release property. It had been found that the release rate and extent of intercalated drug was closely linked to the retarding status of LDH interlayer, which was dependent on the exchange mole ratio of n(drug) with n[HnPO4(3-n)-]. In addition, the grafting reaction and phase transformation degree of LDH layer was hinged on the acidity of solution. The slow-release function of the LDH-drug system could be improved significantly by compositing with dextran (DET). A sustained-release skeleton tablet was producted with DET-LDH-ASP drug delivery system and hydrophilic gel material HPMC, which could effectively overcome the "first pass effect" and " burst release problem" of LDH-drug oral agents. The slow-release effect of LDH drug delivery system could be ulteriorly improved in systemic circulation environments, attributed to the triple control of HPMC-DET-LDH, DET-LDH-drugs three-level supramolecular assembly and the special circulation in vivo.
Key words: Layered double hydroxide, Supramolecular assembly, Release control, Slow controlled release drug delivery system

Abstract: Zinc layered hydroxides (ZLHs) can be used as host materials for drug-ZLH host–guest structures. Aspirin with 0.1 and 0.4 M were intercalated into zinc layered hydroxides to form aspirin nanocomposites; ASPN1 and ASPN4, respectively. From XRD and software, the interlayer spacing of ASPN1 and ASPN4 was 15.2 Å. The result coupled with molecular geometry calculation indicates that the spatial orientation of the drug in the ZLH was monolayer for ASPN1 and ASPN4 nanocomposites. The release of the aspirin from ASPN4 nanocomposite at pH 6.8 is 35%, compared to 98% at pH 1.2, and followed Hixson model and Korsmeyer model for ASPN4 at pH 6.8 and pH 1.2, respectively. This result indicates sustained release of the drugs from their respective nanocomposites, and therefore these nanocomposites have good potential to be used as controlled-release formulation of the aspirin. The ASPN4 nanocomposite was highly effective to Escherichia coli compared to free aspirin, where the ASPN4 given 1.37 inhibition zone compared to aspirin which given 1.17 cm inhibition zone.